This specification covers standard specification for several grades of minimum-wall-thickness, seamless and welded, carbon and alloy-steel tubes intended for use at low temperatures. The steel shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, copper, cobalt, and molybdenum. The number of tubes in a heat-treatment lot shall be determined from the size of the tubes. The tubes shall have a hardness number that does not exceed the prescribed Rockwell and Brinell hardness values. Several grades of steel shall conform to the following tensile properties: tensile strength, yield strength, and elongation. For Grades 1, 3, 6, 7, and 9, the notch-bar impact properties of each set of three impact specimens, including specimens for the welded joint in welded pipe, shall not be less than the prescribed values. Several mechanical tests shall be conducted, namely: flattening test; flare test (seamless tubes); flange test (welded tubes); reverse flattening test; hardness test; and impact tests. Hydrostatic or nondestructive electric test shall also be performed. Materials shall be tested for impact resistance at the prescribed temperature for the respective grades. Impact temperature reduction values shall be by any amount equal to the difference between the temperature reduction corresponding to the actual material thickness and the temperature reduction corresponding to Charpy specimen width actually tested.

1.1 This specification covers several grades of minimum-wall-thickness, seamless and welded, carbon and alloy-steel tubes intended for use at low temperatures. Some product sizes may not be available under this specification because heavier wall thicknesses have an adverse affect on low-temperature impact properties.

1.2 Supplementary Requirement S1 of an optional nature is provided. This shall apply only when specified by the purchaser.

Note 1—For tubing smaller than 1/2 in. [12.7 mm] in outside diameter, the elongation values given for strip specimens in Table 1 shall apply. Mechanical property requirements do not apply to tubing smaller than 1/8 in. [3.2 mm] in outside diameter and with a wall thickness under 0.015 in. [0.4 mm].

1.3 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. The inch-pound units shall apply unless the "M" designation of this specification is specified in the order.